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<H4 CLASS="Head3">
<A NAME="pgfId-193394"></A>USER_DATA</H4>
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<A NAME="pgfId-193395"></A>The <A NAME="marker-199675"></A>USER_DATA policy applies to the <A NAME="marker-268164"></A>domain participant, <A NAME="marker-268169"></A>data reader, and <A NAME="marker-268174"></A>data writer entities via the <EM CLASS="Code">
user_data</EM>
 member of their respective QoS structures. Below is the IDL related to the user data QoS policy:</LI>
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<P CLASS="Code">
<A NAME="pgfId-193396"></A><EM CLASS="Code">
</EM>
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<A NAME="pgfId-193397"></A><EM CLASS="Code">
struct UserDataQosPolicy {</EM>
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<A NAME="pgfId-193398"></A><EM CLASS="Code">
  sequence&lt;octet&gt; value;</EM>
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<A NAME="pgfId-193399"></A><EM CLASS="Code">
};</EM>
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<A NAME="pgfId-199682"></A>&nbsp;</P>
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<A NAME="pgfId-268194"></A>By default, the <EM CLASS="Code">
value</EM>
 member is not set. It can be set to any sequence of octets which can be used to attach information to the created entity. The value of the USER_DATA policy is available in respective <A NAME="marker-268385"></A>built-in topic data. The remote application can obtain the information via the built-in topic and use it for its own purposes. For example, the application could attach security credentials via the USER_DATA policy that can be used by the remote application to authenticate the source.</LI>
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